Information on intermolecular potentials obtained from the temperature dependence of the ir absorption spectrum of rare gas mixtures

The infrared collision-induced absorption spectra of He-Kr and He-Xe mixtures were measured at 300° and at 620°K. The results were analyzed in terms of models previously suggested by Levine and Birnbaum and by Okada et al. The integrated intensities are found to be strongly temperature dependent. This finding indicates the molecules are actually soft. It is definitely concluded that studies of the temperature dependence of collision-induced absorption spectra can be used to obtain information on intermolecular potentials (particularly their repulsive part). For the case of He-Kr and He-Xe mixtures it is found that the results support the modified Buckingham exp-6 potential in preference to the LennardJones potential.